I recently built a DIY power amp and i am using Buffalo 32s as analog source. I am planning to have a DIY solution to replace my old integrated amp that i am using as preamplifier between B32s and the amp. One solution would be to use B32s as preamplifier and use digital volume control, such as Volumite. I am assuming that the analog section driven with dual mono Placids would be sufficient to drive the power amp's input.

However, the preamplifier must be able to do the following:
- volume control
- left-right balance
- Volume level display
- Remote control

I have been thinking of using something like PRM-1 module on this page - http://www.bentaudio.com/index2.html (OEM / DIY TAP Modules section)- to replace Volumite. The PRM-1 module would meet all the requirements above. I am assuming the PRM-1 module works as stereo attenuator, which would be same as there were separate volume pots for left and right channels.

But how big a job you think it would be to build a custom control firmware/controller for B32s to use a custom unit like that? Does the Volumite work like this - The microcontroller interfaces into the audio stream from I2C socket and basically just attenuates the digital samples?

But since there are different firmware for different TPA DACs that makes me wonder that what device specific stuff is there? Or does Volumite just change some register values on the DAC chip which vary between products? Are there documents for the interface available somewhere (for Buffalo 32s) or even the firmware source code?

ps. I have around 25 years of programming experience. None of that comes from programming microcontrollers tho. Would be interesting to try something like that...

Edited by user Saturday, February 20, 2010 6:35:50 AM(UTC)  | Reason: Not specified

Thanks! I did not realize that the soon-to-be-released "Audio Controller 1" and "Femto Processing Core" in the Web were exactly what i need. I guess i'll just wait until the AC1/Femto release and use the integrated as preamp until then.

Edited by user Saturday, February 20, 2010 8:04:28 AM(UTC)  | Reason: Not specified

Try Arduino. I'm not a s/w guy but with the help of the Arduino community I was able to built a control for the OPUS DAC with LCD display and IR remote.

You will also need to request a datasheet from your local distributor and sign an NDA (seems just a formality or sales/marketing thing)

The registers are in the datasheet.

I actually just redesigned the AC1 board (femto has been finished for quite a while).

The biggest barrier to ESS applications is that I would have to break the NDA to publish all the source code... That's a bummer. I am hoping ESS will change it's policy soon.

AC1 is very simple to use, programming is via USB.

Thanks, i kinda found it with google already tho ;). The remote and display controlling parts might come useful. Also there was also an example how to use the i2c interface. I would not mind seeing the wirings with arduino tho. I calculated 2 outputs for i2c, 1 input for remote and 10 inputs for display, plus some power pins and grounds used. If i am right and you did not use the mega version or arduino, i should have 1 pin left in the i/o side.

I sent the signed NDA to ESS as well (through local sales rep), lets see if/when i get the secret datasheet :). Arduino has been ordered, also the display and the remote. So everything is quite ready. Would be cool to get this thing going.

Brian & Russ:
One more thing that worries me tho is that if the onboard controller chip cannot be used together with i2c hardware connected how complex stuff exactly is in that firmware. Does it just initialize the chip according to the jumpers and set the volume levels for channels or is there more to it?

Does this mean that there'll be no AC1 until ESS remove the requirement for an NDA? That's bad news

Could there be some arrangement whereby all buyers sign the NDA? The Arduino looks good but complicated. I'd much rather have a TP solution as then I'd know it would work 'out of the box'.

HI Nic,

Thats pretty much what we have in mind. :)

Correct.

Ok, i have built driver for my old SD5708 led matrix display for Arduino. I got the IR receiver working, with some random IR receiver i bought for a couple euros. I also built a simple UI for setting volume, balance, and some other settings with remote control.

But, i cannot get the I2C working. I removed the onboard firmware and connected (Arduino analog pin 4)SDA->(B32s)SDA and (Arduino analog pin 5)SCL->(B32s)SCL pins.

The b32s does not seem to take any commands in and after several commands sent the Wire.endTransmission() just freezes. That function does that actual transfer. I built pretty solid cables between the devices and soldered them in place so poor connection shouldn't be the problem. And after rechecking 100 times, i am very certain the wirings are good.

I also figured that Wire Api shifts I2C device id one bit right to add R/W bit in (7 bit devide id), but fixing that did not help either. Then i thought maybe its the power from USB, so i hooked up LCDPS @ 9V to power Arduino. Still no go.

I am getting pretty clueless here, but I hope its just some stupic mistake I've made and not a incompability problem.

Questions:

Is there something else i need to take care of to enable the I2C on B32s side? Just take off the firmware and connect the I2C pins?

Are there 4.7k resistors in B32s for I2C? I read some people are using those with Arduino and I2C. Looking at Volumite's schematics, there are some 2.2K pull up resistors. Do i need to add those to SDA and SCL lines?

Edited by user Sunday, February 28, 2010 10:08:49 AM(UTC)  | Reason: Not specified

Thank you! I got it working.

It was the GND line that was missing. All the other I2C applications i tried to learn used two wires and since the whole thing is based on "Two Wire Interface" aka TWI, I just didn't realize GND between the devices was needed as well.

Anyways, i am glad the problem was a trivial one.

Edited by user Sunday, February 28, 2010 2:08:53 PM(UTC)  | Reason: Not specified